I think you might be missing the point of the triple or quad crossover. The reason for it is that you can set different crossovers in the receiver for the Front, Center, and Surround speakers, where it will send all the bass below that frequency to the sub. So, for example, if you have a VP150, M60s, and QS8s, you could set the Fronts to 60 Hz, the Center to 90 Hz, and the QS8s to 80 Hz, thereby using all the speakers to their full extent. Whether this is necessary or desirable is another question (see Alan's comments in another current thread), but it is a valuable feature. That way, you're not cutting your M60s off at 90 Hz or missing the bass below 85 Hz in the center channel of your source material.
